1. Field of the Invention
The present invention relates to methods and apparatus for erecting tubular carton blanks from a flattened configuration to an open tubular configuration.
2. Description of the Related Art
Machines for packing solid articles or for packing liquids are often designed to be fed with a supply of carton blanks in an open tubular configuration. During the packing operation, a bottom closure is formed, the blank is filled with the appropriate contents and a top closure is formed to produce a filled box. The tubular blanks are generally supplied to the machine in flattened form from a magazine containing a stack of such flattened blanks. The blanks must be removed one by one from the magazine and must be erected into an open tubular configuration for packing as described above. Numerous proposals have been made in the past for carrying out the steps of removing the flattened blanks from the magazine and opening them whilst positioning them in a packing machine for filling and closing. In EP-A-0425226, blanks are removed at the mouth of a magazine by a transfer wheel which has several similar transfer arms. Each arm has a hook to engage the trailing edge of a blank at the magazine mouth and to drive the magazine sideways out of the mouth whilst the face of the blank is engaged by a suction head which grips the blank. After the rotating arm clears the magazine, the hook is rotated round with respect to the suction head forcing the blank to open by hinging movement of panels of the blank with respect to one another about a line joining respective panels which lies between the suction head and the hook. The opened blank is carried round on the transfer arm to a conveyor having a succession of pockets and the opened blank is deposited into a respective pocket on the conveyor.
This effectively restricts the orientation of the openings of the pockets to facing out from their conveyor, but in some circumstances it is desirable for the cartons to be in pockets in which the openings face forwards or backwards along the direction of movement of the conveyor.
Broadly similar arrangements for extracting blanks from a magazine, opening them and depositing them on a moving conveyor for further handling are described in numerous other specifications such as GB-A-2053133. In all of these previously described arrangements, the carton blanks are delivered into the conveyor pockets in an erected state.
An alternative scheme is shown in U.S. Pat. No. 3,937,458 and used also in U.S. Pat. No. 4,642,975. Here, blanks are withdrawn from the mouth of a magazine by a suction cup which is driven by an epicyclic gear mechanism to move over an approximately triangular path, one apex of which coincides with the magazine and a second apex of which coincides with the path of a pocket conveyor into which articles drawn from the magazine are to be dropped. It is disclosed that by arranging for the blanks withdrawn from the magazine to contact a suitable striker carried by the conveyor mechanism, the blanks may be forced to open as they are deposited into a pocket on the conveyor.
In the arrangement described, it will be difficult to operate at any substantial speed because the blank is removed out of the magazine after attachment to a suction cup which where it contacts the lead blank in the magazine, is undergoing virtually a reciprocating movement. Also, the erection of the blank depends upon contact between the blank and the moving conveyor. The speed of the apparatus is therefore limited by the speed at which one can open a carton blank in this manner without damage.